5.Are you, tall
6.is, young his friend
7.Is she, fat,her, brother,she's thinner
9.am good, do
10.Do, fly, higher, fly, lower, him
11.swimming, friends swim slower
13.Do,sing better than, do
15.Do, play, better,play,well
18.is, short, buy,bigger/larger
19.not,tall (但这样改来,意思变了.应该是:Mike is not as tall as me.)